The 2020 WAN takes shape -- SDN, virtualization, and hybrid WANs

Hank Levine |
Aug. 17, 2015

It’s not clear how fast MPLS will go the way of Frame Relay and ATM, but changing apps and bandwidth needs will force enterprises to embrace a new set of technologies.

The obvious -- but not only -- payoff from this is the ability to bring branches and other remote sites on line quickly and inexpensively in places where broadband dedicated access is expensive or can take a long time to implement or both (e.g., when you want Ethernet Access at a site and discover there's no fiber to the building and it will take 6 months and $25,000-$100,000 to get it there).

Hybrid WANs can also make better use of wireless LTE access, even to MPLS, and they allow users to allocate premium MPLS bandwidth to applications that really need it, mitigating the need for costly port or circuit upgrades or allowing for a reduction in MPLS bandwidth (and cost). For many enterprises, a hybrid-WAN is also a way to begin abandoning the back-haul architecture that MPLS networks often employ to access Internet based services.

Hybrid WANs predate SDN, and can be implemented without SDN. But setting up policy based routing and the right mix of traffic off-load required engineering expertise and was relatively static. SDN makes it possible to manage and route globally from a single location/controller, and considerably enhances the hybrid-WAN concept.

As already mentioned, SDN's centralized control/management facilitates simpler and easier configuration and oversight of branches or remote locations, including: much improved path selection/prioritization; better monitoring; cheaper CPE; and simpler/faster upgrades (because if you're changing a control function you only have to update one machine, not dozens or hundreds). In sum, SDN makes hybrid WANs compelling.

Issues? What issues?

There are several:

The CapEx associated with new hardware and software. Fortunately, engineers have figured out how to combine SDN and traditional networks, which allows for gradual transition rather than expensive and nail-biting flash cuts.

A shortage of SDN-conversant engineers. It happens every time there's a network technology transition. Give it a few years. In the meantime, this means that most initial deployments will be on a managed services basis, dominated by the major carriers and systems integrators.

Service Levels. Internet access (like mobile services) comes without meaningful SLAs. That drives network engineers nuts (their spiritual ancestors are all Bell System geeks). But the absence of service levels in the transport layer doesn't necessarily kill quality of service; it just means that you engineer it through network controllers using their ability to prioritize, optimize paths, route around network congestion/failure, etc. If you just can't abide the idea of consumer-like broadband offerings, dedicated Internet access can provide a comforting half-way house -- it offers meaningful SLAs, but at a price.

Bandwidth and Contention. With cable broadband service a set of interconnected subscribers typically share a connection to the closest node. This means that the traffic from one site contends with (and its speed can be compromised by) traffic from other sites connected to the same node. The issue is most relevant to consumer broadband services, where the difference between uplink and downlink speeds needs to be factored into bandwidth requirements. In the future, high speed fiber-to-the-premise services like Google Fiber (1Gbps) could have a huge impact here, but as yet these are not widely available.

Broadband Availability. Internet connectivity using broadband cable remains close to its residential roots and consumer focus, meaning that business-class cable connectivity is not ubiquitously available even at corporate locations within a cable provider's franchise territory.

Contracts. Yes, they'll look different. To give just two examples, you need to A) develop and negotiate controller SLAs that take into account the benefits of SDN engineering as well as the usual transport SLAs; and B) plan/time the transition to an SDN WAN so you don't incur shortfall or early termination charges on your existing infrastructure. There is also going to be a transition involving what enterprises are offered or may have to accept for very low cost broadband circuits compared to highly negotiated, less carrier-biased MPLS contracts. If you're nervous we're here to help.